#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn = ;
int n,x[maxn];
int cmd,cnt,ans,max_x;
int main(){
freopen("box.in","r",stdin);
freopen("box.out","w",stdout);
ios::sync_with_stdio(false);
cin>>n;
for(int i = ;i <= n;i++){
cin>>cmd;
x[cmd]++;
max_x = max(max_x,cmd);
}
while(){
cnt = ;
for(int i = ;i <= max_x;i++){
while(x[i] && i >= cnt){
x[i]--;
cnt++;
}
}
if(!cnt) break;
ans += ;
}
cout<<ans;
return ;
}